<?php
/**
 * Created by PhpStorm.
 * User: User
 * Date: 2017/9/20
 * Time: 8:28
 */

$num1=isset($_POST['num1']) ? $_POST['num1'] : "";
$num2=isset($_POST['num2']) ? $_POST['num2'] : "";



echo "<form><input id='t1' type='text' value=\"<?php echo $num1;?>\">"."<select name=\"\"> 
<option value=\"+\">+</option>
<option value=\"-\">-</option> 
<option value=\"*\">*</option> 
<option value=\"/\">/</option> 
</select> "."<input id='t2' type='text' value=\"<?php echo $num2;?>\">".'='."<input type='text'>"."<button>计算</button></form>";



